need to lock around completion and watcher hashes
need to lock around completion and watcher hashes

There's the possiblity for inconsistent views of the callbacks because
of the way locking and contexts are handled

zk-ruby/zookeeper,rickypai/zookeeper,rickypai/zookeeper,rickypai/zookeeper,songling88/zookeeper,songling88/zookeeper,rickypai/zookeeper,zk-ruby/zookeeper,zk-ruby/zookeeper,songling88/zookeeper,songling88/zookeeper